Internal and External Validity Considerations in Vocabulary Studies

The crucial role of validity in research has been well recognized for utilization of the findings and making sound decisions. However, in relation to the educational contexts such as Iran, where each year a large number of students are admitted to MA and Ph. D. programs, little is known about how these students conduct their studies. Also given that vocabulary is one of the most important components of reading comprehension and a predictor of language proficiency, this study was undertaken to review factors contributing to internal and external validity of vocabulary studies and examine the rigor with which these studies are conducted. For this purpose, 15 studies from Iranian Journals published between 2014-2015 were examined based on the Internal and External Validity Criteria Checklist proposed by Leow (1999). The findings indicated that Iranian researchers are less concerned with internal validity than external validity mainly for practicality reasons. The paper concludes with implications and recommendations for further research in relation to findings.